ON THE USE OF FFT ALGORITHM FOR THE CIRCUMFERENTIAL CO-ORDINATE IN BOUNDARY ELEMENT FORMULATION OF AXISYMMETRIC PROBLEMS

A new numerical method is proposed for the boundary element analysis of axisymmetric bodies. The method is based on complex Fourier series expansion of boundary quantities in circumferential direction, which reduces the boundary element equation to an integral equation in (r–z) plane involving the Fourier coefficients of boundary quantities, where r and z are the co-ordinates of the (r, θ, z) cylindrical co-ordinate system. The kernels appearing in these integral equations can be computed effectively by discrete Fourier transform formulas together with the fast Fourier transform (FFT) algorithm, and the integral equations in (r–z) plane can be solved by Gaussian quadrature, which establishes the Fourier coefficients associated with boundary quantities. The Fourier transform solution can then be inverted into (r, θ, z) space by using again discrete Fourier transform formulas together with FFT algorithm. In the study, first we present the formulation of the proposed method which is outlined above. Then, the method is assessed by using three sample problems. A good agreement is observed in the comparisons of the predictions of the method with those available in the literature. It is further found that the proposed method provides considerable saving in computer time compared to existing methods of literature. © 1997 by John Wiley & Sons, Ltd.     

QUALITY CHARACTERISTICS OF CORN NOODLES CONTAINING GELATINIZED STARCH, TRANSGLUTAMINASE AND GUM

ABSTRACT

Effects of gelatinized corn flour addition level (40, 60 and 80%), gum (locust bean gum or xanthan gum, 3%) and/or transglutaminase (TG, 0.5%) on quality characteristics of corn noodle were investigated. Gelatinized corn flour was used as a binder for remaining untreated corn flour (60, 40 and 20%). Corn noodles were evaluated in terms of cooking properties (cooking loss, total organic matter (TOM), water absorption, swelling volume and maximum force), color, sensory and pasting properties. Noodle sample containing gelatinized corn flour at level of 80% exhibited best cooking and sensory properties. Gum and/or TG were added to this noodle formula. Gum improved noodle quality in terms of some cooking properties. Improving effect of xanthan gum was more obvious. Covalent crosslinks catalyzed by TG caused significantly lower cooking loss and TOM values. Gums generally caused increases in Rapid ViscoAnalyzer viscosity values of noodles. Gum and/or TG show great promise in processing of gluten‐free corn noodle.

PRACTICAL APPLICATIONS

Celiac disease occurs in about one in 300 people in Europe. Lack of gluten in cereals that are safe for gluten‐free food causes major problems in dough processing and product quality. Technological difficulties in production and lack of awareness of number of celiac patients in need of gluten‐free products might restrict researches related to gluten‐free food. In recent years, various approaches to overcome the technological problems are arising. Searching for ingredients that have ability to mimic properties of gluten in production of gluten‐free food is the most common approach. We report herein beneficial effects of gelatinization, gum (locust bean gum, xanthan gum) and/or transglutaminase (TG) in gluten‐free corn noodle production. They have major improving effects in noodle quality and show great promise as a processing aid in bulk manufacture of gluten‐free corn noodle. To the best of our knowledge, there is no study investigating utilization of TG in gluten‐free corn noodles.     

Investigation of diffusion kinetics of plasma paste borided AISI 8620 steel using a mixture of B 2 O 3 paste and B 4 C/SiC

In the present study, AISI 8620 steel was plasma paste borided by using various B₂O₃ paste mixture. The plasma paste boriding process was carried out in a dc plasma system at temperatures of 973, 1023 and 1073 K for 2, 5 and 7 h in a gas mixture of 70% H₂ -30% Ar under a constant pressure of 10 mbar. The properties of the boride layer were evaluated by optical microscopy, X-ray diffraction, Vickers micro-hardness tester and the growth kinetics of the boride layers. X-ray diffraction analysis of boride layers on the surface of the steel revealed FeB and Fe₂B phases. Depending on temperature and layer thickness, the activation energies of boron in steel were found to be 124.7 kJ/mol for 100% B₂O₃.     

The effect of a sliding load on strain gauges embedded under the contact surface

Strain gauges embedded in plastic models can be used in three dimensional stress analysis. When gauges are located immediately below a surface subjected to the tangential traction of a sliding load, unexpected values are recorded. This phenomenon was investigated by suitably loading a semi–infinite solid with normal and shear stresses and comparing theoretical strain values with the experimental results. The comparison showed that strain gauges embedded in epoxy can be successfully used under sliding loads provided that the gauge depth below the contact surface is greater than a critical value.     

便携式应用领域电源MOSFET的选择

随着封装技术和硅工艺的进步,具有更高电源密度和更高效率的小尺寸MOSFET正在逐步克服原来与器件尺寸相关的电源处理能力和处理效率问题。